Components of various industrial devices are often subjected to extreme conditions, such as high-temperatures and high-impact contact with hard and/or abrasive surfaces. For example, extreme temperatures and pressures are commonly encountered during earth drilling for oil extraction or mining purposes. Diamond, with its unsurpassed mechanical properties, can be the most effective material when properly used in a cutting element or abrasion-resistant contact element for use in earth drilling. Diamond is exceptionally hard, conducts heat away from the point of contact with the abrasive surface, and may provide other benefits in such conditions.
Diamond in a polycrystalline form has added toughness as compared to single-crystal diamond due to the random distribution of the diamond crystals, which avoids the particular planes of cleavage found in single-crystal diamond. Therefore, polycrystalline diamond (PCD) is frequently the preferred form of diamond in many drilling applications. A drill bit cutting element that utilizes PCD is commonly referred to as a polycrystalline diamond cutter (PDC). Accordingly, a drill bit incorporating PCD cutting elements may be referred to as a PDC bit.
PCD elements can be manufactured in a press by subjecting small grains of diamond and other starting materials to ultrahigh pressure and temperature conditions. One PCD manufacturing process involves forming polycrystalline diamond directly onto a substrate, such as a tungsten carbide substrate. The process involves placing a substrate, along with loose diamond grains mixed with a catalyst binder, into a container of a press, and subjecting the contents of the press to a high-temperature, high-pressure (HTHP) press cycle. The high temperature and pressure cause the small diamond grains to form into an integral PCD intimately bonded to the substrate.
Once formed, the PCD element can then be attached to a drill bit via the substrate. Due to difference in materials properties such as wettability, a substrate is typically easier to bond to another surface than diamond is when using certain methods. For example, a PCD element can be attached at its substrate to the drill bit via soldering or brazing, whereas PCD without a substrate could not be easily bonded to a drill bit with sufficient strength to withstand the conditions of drilling. Soldering and brazing may be performed at relatively low temperatures at which the PCD portion of the element remains stable, so that the PCD portion is not adversely affected by the process of joining to the bit.